In the firearms industry, it has long been the practice to provide cartridge magazines in which each of a plurality of cartridges is generally horizontal, or with its centerline oriented at an angle for being rammed into the chamber of the barrel and wherein all the rounds are vertically stacked. A follower on the upper end of a coil spring supports the vertical stack of rounds. In loading the magazine, the rounds are fitted individually into its open, upper end with the first round being disposed on the follower and subsequent rounds being supported by the body of the preceding round. The last loaded, or uppermost round will be the first round to be loaded into the chamber of the gun barrel when the magazine is fitted into the gun to ready the same for firing. After each round is fired, the next and successive rounds are fed upwardly by the follower and coil spring to the uppermost position in the magazine at which each round is disposed prior to being rammed into the chamber of the gun.
Typically, such magazines include lips disposed along the spaced upper edges of the magazine side walls. The lips usually have upper edge portions that extend inwardly from the side walls of the magazine and serve to retain the uppermost round in position in the magazine to be fed into the chamber of the gun barrel. The transfer or feeding of rounds successively from the magazine into the chamber is in response to energy of recoil imparted to the slide which compresses and energizes the recoil spring. That spring expands to return the slide and breech block carried therein to the "ready position" of firing mechanism.
As the breech block is moved toward its "closed" position with the uppermost cartridge in the magazine disposed in its path of movement, the breech block engages the rear surface of the cartridge case a substantial distance above the centerline of the bullet. That distance defines a moment arm whereby the force exerted by the breech block causes the forward end of the round to dip or pitch downward as it moves forwardly. That tendency of the uppermost round is further compounded by the after-end of the upper round being lifted somewhat by upward movement of the penultimate round as it is being thrust upward to replace the top round. Upon the top round being rammed toward the breech clears the front wall of the magazine, it engages an inclined ramp on the frame at the breech end of the barrel for guiding the round upwardly into the chamber of the barrel.
The dimensions and configuration of a magazine are selected for use in the particular gun in which the magazine is to be used and with conventional size rounds. The drawbacks of using with this type of magazine are generally encountered only when one attempts to use rounds of ammunition, such as flat or hollow nose bullets, which are substantially shorter in length than conventional rounds. In particular, during that portion of the loading cycle whereby each round is transferred, or fed from the magazine into the chamber of the pistol barrel, the shorter rounds have a greater tendency to engage the forward wall of the magazine tube wall. When this occurs, a serious jam can result which prevents proper loading and firing of the gun.
Past attempts to prevent such jamming, as disclosed in U.S. Pat. Nos. 2,895,248 and 5,153,359, have included a tab 50 disposed on the outer end of a separate element 38 or a ramp 64 on the upper edge of the forward wall 46 of a magazine 10. Such ramps or tabs, as disclosed in the prior art, may help to prevent shorter rounds from becoming jammed against the tube wall or during feeding. This type of solution has not, however, solved the problems of such rounds jamming against the barrel feed ramp.
Moreover, that type of solution has not generally proven totally effective, especially if used in conjunction with a fixed barrel, as contrasted with a dropping barrel in which the breech is actually lowered towards the upper edge of the magazine tube. In the former situation, the fixed breech remains vertically offset a relatively large distance from the upper edge of the magazine tube and, as a result, if the round does not approach the feed ramp at the proper angle, a jam may result.
Indeed, in recent years, with the advent of semi-automatic handguns, such as high powered compact pistols of the 0.45 caliber and 9 mm types, the instances of jamming and cartridge feed malfunctioning have increased markedly. U.S. Pat. No. 5,014,456 assigned to Smith & Wesson Corp., the same assignee as this Application, carefully analyzed the problems associated with greater recoil velocity and cartridge feed malfunctions and pistol jamming. It was found that because of the greater kinetic energy of the slide, upon its impacting against the frame, a greater tendency was noted on recoil of such pistols for the upper cartridges to shift or move forward in the magazine. As a result, the uppermost round may not only be disoriented which renders problematic its accurate feeding to the chamber of the barrel but in some extreme cases, the round may even be dislodged from the magazine.
The above referenced U.S. Pat. No. 5,014,456 sought to provide a solution for such dislodgement problems by providing control and guide means to retain the upper round so that it is unable to shift forwardly or otherwise out of proper alignment for feeding into the barrel. The same means also acted to cam the penultimate round so it will be properly repositioned for its movement to the top position in the magazine.